In a mobile communication system such as a cellular phone, a communication system of an LTE (Long Term Evolution type) method which reduces transmission delay and connection delay than usual is spreading.
An entire structure of a radio access network in the mobile communication system of the related LTE method (E-UTRAN: Evolved Universal Terrestrial Radio Access Network) will be described with reference to FIG. 12.
A mobile communication system 1001 of the LTE method includes: a mobile station 1050 called as UE (User Equipment), and a radio base station 1060 called as eNB (E-UTRAN Node B). Between the mobile station 1050 and the base radio station 1060, communication is performed via a radio link (RL) 70.
The mobile station 1050 includes: a PDCP (Packet Data Convergence Protocol) sublayer 1051, an RLC (Radio Link Control) sublayer 1052, an MAC (Medium Access Control) sublayer 1053, a Physical layer 1054 and a radio unit 1055. The radio base station 1060 includes: a PDCP sublayer 1061, an RLC sublayer 1062, a MAC sublayer 1063, a physical layer 1064 and a radio unit 1065.
Next, a structure of the RLC sublayer 1062 in the radio base station 1060 and the RLC sublayer 1052 in the mobile station 1050 of the related mobile communication system 1001 will be described with reference to FIGS. 13 and 14.
The RLC sublayer 1062 in the radio base station 1060 includes: an RLC_SDU (Service Data Unit) receiving unit 1080, a transmission buffer 1081, an RLC_PDU (Protocol Data Unit) generating unit 1082, an RLC_PDU transmitting unit 1083, a re-transmission buffer 1084, an RLC_PDU receiving unit 1085, a reception buffer 1086, an RLC_SDU generating unit 1087, an RLC_SDU transmitting unit 1088, a transmission control information memory unit 1089 and a reception control information memory unit 1090.
Also, the RLC sublayer 1052 in the mobile station 1050 includes: an RLC_PDU receiving unit 1100, a reception buffer 1101, an RLC_SDU generating unit 1102, an RLC_SDU transmitting unit 1103, a re-transmission buffer 1104, an RLC_SDU receiving unit 1105, a transmission buffer 1106, an RLC_PDU generating unit 1107, an RLC_PDU transmitting unit 1108, a transmission control information memory unit 1109 and a reception control information memory unit 1110.
Next, processing of the RLC sublayer 1052 in the mobile station 1050 and the RLC sublayer 1062 in the radio base station 1060 of the mobile communication system 1001 shown in FIG. 12 will be described with reference to FIGS. 12 to 14. Concerning the processing of the RLC sublayers 1052 and 1062, although there are TM (Transparent Mode), UM (Unacknowledged Mode) and AM (Acknowledged Mode), it will be described with AM below.
As shown in FIG. 12, in a part in which transmission processing is performed in the mobile station 1050 (a part shown with down arrow in the figure), for transmitted C/U plane data, that is, control plane data or user plane data (hereinafter, referred to as data), PDCP processing by the PDCP sublayer 1051, RLC processing by the RLC sublayer 1052, MAC processing by the MAC sublayer 1053 and physical processing by the physical layer 1054 are applied in turn, and data to be transmitted is created. The transmission data is transmitted to the radio link 70 by the radio unit 1055 as a radio signal.
Also, in a part in which reception processing is performed in the mobile station 1050 (a part shown with up arrow in the figure), the radio signal from the radio link 70 is received by the radio unit 1055, and for the received signal, physical processing by the physical layer 1054, MAC processing by the MAC sublayer 1053, RLC processing by the RLC sublayer 1052 and PDCP processing by the PDCP sublayer 1051 are applied to the received data in turn. From the data to which a series of processing is applied, data transmitted from the transmission-side is extracted (received).
Also in a part in which transmission processing is performed in the radio base station 1060 (a part shown with up arrow in the figure), for the data transmitted, PDCP processing by the PDCP sublayer 1061, RLC processing by the RLC sublayer 1062, MAC processing by the MAC sublayer 1063 and physical processing by the physical layer 1064 are applied in turn. Data to which a series of processing is applied is transmitted to the radio link 70 by the radio unit 1065 as a radio signal.
Also in a part in which reception processing is performed in the radio base station 1060 (a part shown with down arrow in the figure), the radio signal from the radio link 70 is received by the radio unit 1065, and for the received data physical processing by the physical layer 1064, MAC processing by the MAC sublayer 1063, RLC processing by the RLC sublayer 1062 and PDCP processing by the PDCP sublayer 1061 are applied in turn. From the data to which a series of processing is applied, data transmitted from transmission-side is extracted (received).
As shown in FIGS. 13 and 14, the RLC_SDU receiving unit 1080 of the RLC sublayer 1062 in the radio base station 1060 receives RLC_SDU from the PDCP sublayer 1061 and stores it in the transmission buffer 1081. The RLC_PDU generating unit 1082 acquires data required for transmission from the transmission control information memory unit 1089, the re-transmission buffer 1084 and the transmission buffer 1081, and generates RLC_PDU.
When the RLC_PDU generating unit 1082 generates RLC_PDU, the RLC_PDU generating unit 1082 adds RLC_SN (Sequence Number) to an RLC header. The RLC header includes a polling bit. By setting the polling bit, a report of receiving condition of the mobile station 1050 is requested.
Generated RLC_PDU is, in preparation for ARQ (Automatic Repeat request) re-transmission, stored in the re-transmission buffer 1084 and transmitted to the MAC sublayer 1063 in the radio base station 1060 by the RLC_PDU transmitting unit 1083. RLC_PDU transmitted to the MAC sublayer 1063 is sent to the radio unit 65 via the physical layer 1064. RLC_PDU is sent to the mobile station 1050 via the radio link 70 from the radio unit 1065.
In the mobile station 1050, RLC_PDU sent from the radio base station 1060 is received by the radio unit 1055 via the radio link 70. Received RLC_PDU is received, via the physical layer 1054, by the RLC_PDU receiving unit 1100 of the RLC sublayer 1052 from the MAC sublayer 1053 in the mobile station 1050.
The RLC_PDU receiving unit 1100 stores, among RLC_PDU received from the MAC sublayer 1053, transmission control information from the radio base station 1060 in the reception control information memory unit 1110 and stores other information in the reception buffer 1101.
The RLC_SDU generating unit 1102 acquires RLC_PDU from the reception buffer 1101 and generates RLC_SDU. Generated RLC_SDU is transmitted to the PDCP sublayer 1051 in the mobile station 1050 from the RLC_SDU transmitting unit 1103.
Also, in case received RLC_PDU includes a request to report receiving condition, or in case it includes a request to detect reception failure and to report receiving condition, the reception buffer 1101 stores information of “request to report receiving condition” or “request to detect reception failure and to report receiving condition” among the received RLC_PDU in the transmission control information memory unit 1109.
Also, the transmission control information memory unit 1109 forwards information of “request to report receiving condition” or “request to detect reception failure and to report receiving condition” stored in the transmission control information memory unit 1109 to the RLC_PDU generating unit 1107.
When the RLC_PDU generating unit 1107 receives information of “request to report receiving condition” or “request to detect reception failure and to report receiving condition” forwarded from the transmission control information memory unit 1109, it prepares for generation of transmission control information. The RLC_PDU generating unit 1107 generates, while generating RLC_PDU, transmission control information which replies to “request to report receiving condition” or “request to detect reception failure and to report receiving condition”.
As stated above, in the RLC_PDU generating unit 1107, transmission control information which notifies whether or not the mobile station 1050 has received RLC_PDU by using RLC_SN as ACK (ACKnowledgement)/NACK (Negative ACKnowledgement) is generated.
Processing in data transmission from the mobile station 1050 to the radio base station 1060 is similar to the processing in data transmission from the radio base station 1060 to the mobile station 1050. That is, the RLC_SDU receiving unit 1105 of the RLC sublayer 1052 in the mobile station 1050 receives RLC_SDU from the PDCP sublayer 1051 in the mobile station 1050 and stores it in the transmission buffer 1106. The RLC_PDU generating unit 1107 acquires data required for transmission from the transmission control information memory unit 1109, the re-transmission buffer 1104 and the transmission buffer 1106 and generates RLC_PDU.
When the RLC_PDU generating unit 1107 generates RLC_PDU, the RLC_PDU generating unit 1107 adds RLC_SN to an RLC header. The RLC header includes a polling bit. By setting the polling bit, a report of receiving condition of the radio base station 1060 is requested.
Generated RLC_PDU is, in preparation for ARQ re-transmission, stored in the re-transmission buffer 1104 and transmitted to the MAC sublayer 1053 in the mobile station 1050 by the RLC_PDU transmitting unit 1108. RLC_PDU transmitted to the MAC sublayer 1053 is sent to the radio unit 1055 via the physical layer 1054. RLC_PDU is sent to the radio base station 1060 via the radio link 70 from the radio unit 1055.
In the radio base station 1060, RLC_PDU sent from the mobile station 1050 is received by the radio unit 1065 via the radio link 70. Received RLC_PDU is received, via the physical layer 1064, by the RLC_PDU receiving unit 1085 of the RLC sublayer 1062 from the MAC sublayer 1063.
The RLC_PDU receiving unit 1085 stores, among RLC_PDU received from the MAC sublayer 1063, transmission control information from the mobile station 1050 in the reception control information memory unit 1090 and stores other information in the reception buffer 1086.
The RLC_SDU generating unit 1087 acquires RLC_PDU from the reception buffer 1086 and generates RLC_SDU. Generated RLC_SDU is transmitted to the PDCP sublayer 1061 in the radio base station 1060 from the RLC_SDU transmitting unit 1088.
Also, in case received RLC_PDU includes a request to report receiving condition, or in case it includes a request to detect reception failure and to report receiving condition, the reception buffer 1086 stores information of “request to report receiving condition” or “request to detect reception failure and to report receiving condition” among the received RLC_PDU in the transmission control information memory unit 1089.
Also, the transmission control information memory unit 1089 forwards information of “request to report receiving condition” or “request to detect reception failure and to report receiving condition” stored in the transmission control information memory unit 1089 to the RLC_PDU generating unit 1082.
When the RLC_PDU generating unit 1082 receives information of “request to report receiving condition” or “request to detect reception failure and to report receiving condition” forwarded from the transmission control information memory unit 1089, it prepares for generation of transmission control information. The RLC_PDU generating unit 1082 generates, while generating RLC_PDU, transmission control information which replies to “request to report receiving condition” or “request to detect reception failure and to report receiving condition”.
As stated above, in the RLC_PDU generating unit 1082, transmission control information which notifies whether or not the radio base station 1060 has received RLC_PDU by using RLC_SN as ACK/NACK is generated.
Above is a communication procedure between the mobile station 1050 and the radio base station 1060 in the related mobile communication system.
A data transmission method which adopts, as mentioned above, automatic repeat request (ARQ) as an error control technology is disclosed, for example, in patent document 1.